Civil defense warning sirens typically include a powered siren or horn which is activated when a weather hazard such as a tornado or hurricane is approaching or is in the vicinity of the siren. Typical prior art sirens are generally powered by electricity which is supplied by a local electric utility power grid. One significant short-coming of this arrangement is it is an approaching tornado can disable the electrical power transmission and distribution means supplying power to a defense siren. Thus, the very event of which a prior art civil defense siren is intended to warn the public may prevent the siren from operating. What is needed is a civil defense siren which will operate when external power is absent.